Re: [bug-libunistring] toCasefold?

[Simon Josefsson]

Bruno Haible <address@hidden> writes:

> Simon Josefsson wrote:
>> >> I'm looking for an implementation of the toCasefold(X) operation defined
>> >> in Unicode 6.0 section 3.13 page 114 [1] like this:
>> >> 
>> >>   R4 toCasefold(X): Map each character C in X to Case_Folding(C).
>> >> 
>> >>   • Case_Folding(C) uses the mappings with the status field value “C” or
>> >>     “F” in the data file CaseFolding.txt in the Unicode Character
>> >>     Database.
>> ...
>> But does u32_casefold match Unicode toCasefold?  Is it possible to
>> disable the SpecialCasing stuff?
>
> SpecialCasing.txt applies to toUpper, toLower, toTitle mappings. For
> toCasefold, all mappings are given in CaseFolding.txt, namely:
>   - the locale independent mappings (type 'C' and 'F'),
>   - the locale dependent mappings (type 'T') - this is similar to
>     SpecialCasing.txt.
>
> u32_casefold uses all of these mappings. And when you pass an empty string
> as ISO639_LANGUAGE, it uses only the locale independent mappings (type
> 'C' and 'F'), hence it matches what toCasefold does.

Thanks -- meanwhile, I manually implemented a simple toCaseFold based on
the tables directly, and now when I compare its output with the output
from u32_casefold it matches for all code points.  So indeed it seems
correct.  Just a data point to boost confidence in your implementation.

/Simon